/Engine/Source/Runtime/GeometryCore/Public/DynamicMesh/DynamicMeshAttributeSet.h
true if the given edge is a seam edge in any overlay. This version considers tangent seams as a type of normal seam; to consider tangent seams separately, call the 4-argument IsSeamEdge instead.
virtual bool IsSeamEdge ( int EdgeID, bool & bIsUVSeamOut, bool & bIsNormalSeamOut, bool & bIsColorSeamOut ) const